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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

A letter to Obama: You still have time to be a climate champion — but not much

Dear President Obama —

I feel a little awkward writing a letter to you, perhaps because I helped organize the largest demonstrations outside your house during your residence there: It’s odd to write someone when the closest you’ve ever come to them is being chained to the fence outside their home protesting the Keystone pipeline.

But I’ve had a very long time to think about global warming — since the late 1980s, when I published the first book for a general audience on the topic of what we then called the greenhouse effect. And so I thought I might offer a few thoughts. It’s only in the last three or four years that climate’s political dimensions have come into clearest focus for me, beginning in some ways with those Keystone demonstrations. As I’ve learned more about how Washington works, I’ve understood better some of the paths you took and didn’t. With 18 months left in your administration, the summing-up mood is appropriate — but not entirely, since time remains for a series of fateful decisions that will shape your legacy, but more importantly the planet’s future atmospheric chemistry.

Bonn meeting ends with last-minute compromise on Paris climate text

Climate change negotiators meeting in Bonn on Thursday came up with a last-minute compromise that observers hope will put the talks on track for a new global agreement on greenhouse gases.

Slow progress was made until the final hours, as nations wrangled over the wording of an 89-page draft text, intending to cut it down to a more manageable size. After two weeks, the text had been cut by just four pages to 85.

But shortly before the talks were scheduled to finish, countries agreed that the co-chairs of the negotiations should be allowed to make their own alterations to the text, and present it to all countries for approval, probably in late July. This should be a quicker process, though there is no guarantee that countries will not try to re-draw the new draft when it becomes available.

BP has threatened to widen a rift between European and US oil companies over how to respond to global warming by urging political leaders to deliver a “substantial” deal at international climate change talks later this year.

Bob Dudley, chief executive of the British oil and gas group, said the United Nations global warming summit in December needed to broker agreements that encourage energy efficiency, renewable power such as wind and the use of gas. Such moves are considered vital if global governments are to succeed in keeping the Earth’s temperatures from rising more than 2C, the internationally agreed threshold to prevent widespread flooding, famine and desertification.

Asked what he wanted to see from the UN conference in Paris, Dudley said:

Something substantial needs to be done. We are conscious of that ... we encourage policymakers to move forward on this when they meet in December.”

Can the divestment movement tame climate change?

An increasingly popular tool in the fight against climate change is emerging - "divestment". The term refers to the shedding of stocks, bonds or other investments, in this case that are held in companies that produce or burn fossil fuels. As the world's leaders prepare for a make-or-break climate summit in November, will divestment change our relationship with fossil fuels - and what might the dangers be, asks our social affairs reporter John McManus?

Climate engineering would cool down the planet — but it may not save West Antarctica

For some time now, fears of climate disaster have been at least partly assuaged by the thought that if the planet really begins to heat up, well, at least we may have a backup plan.

That backup plan is so-called “geoengineering” — artificially altering the planet still further so as to offset warming temperatures. One leading idea in the space is to fill the Earth’s stratosphere with sulfate aerosol particles, which would have a cooling effect by reflecting sunlight back to space. We know this would work because we know that large volcanic eruptions cool the planet, and that they do so by a similar mechanism — firing sulfur high into the skies.

But it’s also very risky — there are many possible unintended consequences of geoengineering. Thus, the only reason to really consider it is if you’re on the verge of climate impacts so severe — impacts like, say, the potential collapse of the West Antarctic ice sheet, leading to 10 or more feet of global sea level rise — that it becomes the lesser evil.

Fossil fuel divestment movement harnesses the power of shame

Norway this month became an unlikely leader in a growing social movement: persuading investors to sell their stock in fossil fuel companies.

In Norway’s case, its $890 billion pension fund — the largest sovereign wealth fund in the world — will begin divesting itself of its stakes in coal companies. The move, approved by Parliament on June 5, offered a powerful endorsement of a tactic its backers say has the potential to reduce carbon consumption and in that way limit harmful greenhouse gas emissions.

The fossil fuel divestment movement, begun on the campus of Swarthmore College in Pennsylvania in 2011, has gathered force in only four years. AXA, the French insurance group, said it would sell $560 million in coal investments. The Rockefeller family said its enormous philanthropic arm would sell fossil fuel investments, starting with coal. And the endowments of several universities, including Stanford and Syracuse, have purged coal company stocks.

It's the planet stupid!: Capitalism and the destruction of the Commons

There is a war going on right now between those who are working to protect the commons and the hard-core capitalists, who are working to privatize our economy, culture, ecology, environment and government.

The stakes are high. The outcome will determine whether we live in a dystopian chaos, or a civil society; whether we preserve our natural life support system, or live on life support.

Xiuhtezcatl Roske-Martinez is 14, but has a confidence beyond his years. He carries on his back an organisation that his mother Tamara founded almost 10 years before his birth, created to inspire young people to defend the environment.

Roske-Martinez is its spokesperson, its youth director, and a self-defined eco hip hop artist, activist and change-agent. He raps. He lectures children younger and older than him at schools around the United States. He rallies before state politicians. And he has addressed world leaders in the United Nations.

Speaking to the Guardian, Xiuhtezcatl explains how his age works to his advantage, and why young people are the fossil fuel industry’s greatest threat.

Oxygen is an overlooked factor in past climate, study suggests

It's well established how carbon dioxide, methane and water vapour affect our climate. But a new study suggests another gas may have played a role in Earth's long climate history - oxygen.

Natural variations in atmospheric oxygen levels could be a missing factor in piecing together Earth's past climate, the researchers say. The findings help explain why climate models tend to simulate temperatures 100m years ago that are lower than scientific evidence suggests.

Rich nations in stalemate over coal subsidy phase-out

Talks on phasing out a form of coal subsidies ended in stalemate as Japan, the biggest user of the aid, led calls for more time in defiance of this week's G7 pledge on fossil fuel subsidies, sources said.

The Paris-based Organisation for Economic Cooperation and Development has been trying for a year to get an agreement from its 34 member nations on phasing out export credits for coal, the most polluting of the fossil fuels.

Sources close to talks in Paris on Wednesday and Thursday, speaking on condition of anonymity, said nations would review the situation over the summer ahead of further talks in September.

Scientists band together, urge Canada to stop tar sands expansion

More than 100 North American scientists released a consensus statement on Wednesday concluding that mining in Canada's tar sands region is destroying the local environment, endangering the rights of indigenous groups and threatening the world's ability to fight climate change—and urging Canadian leaders to curtail their development.

Their statement, 18 months in the making and the first to specifically take a stance on the oil sands, said further development would make it impossible to stave off dangerous levels of climate change. They sent the analysis to Canada’s Prime Minister Stephen Harper and members of Parliament, and requested meetings to discuss the findings.

"We offer a unified voice calling for a moratorium on new oil sands projects," the scientists wrote. "Continued expansion of oil sands and similar unconventional fuels in Canada and beyond is incompatible with limiting climate warming to a level that society can handle without widespread harm."

The Carbon Brief interview: Christiana Figueres

Christiana Figueres has been the executive secretary of the United Nations Framework Convention on Climate Change(UNFCCC) since July 2010 and was reappointed for a second three-year term in July 2013. Before then, she was a member of the Costa Rican negotiating team at the UNFCCC from 1995-2009. In 1995, she founded the non-profit Center for Sustainable Development of the Americas, based in Washington DC.

For two days this week, there is a place in Washington where down is up, and up is down. A place where the globe isn’t warming due to manmade emissions of carbon dioxide and other greenhouse gases, but where evil government-funded scientists are cooking the books to obtain more research grants.

It's a gathering where fossil fuels aren't something to be phased out, as G7 leaders decided to do this week, but rather something to be expanded in order to fight poverty.

This is the morally correct thing to do, advocates say.

You’ve come to the annual International Climate Change Conference, which this year runs Thursday and Friday, just steps from Capitol Hill.

Trust improving in complex UN climate talks, officials say

The latest round of U.N. climate talks in Bonn helped build trust among countries and kept the long trek to a new global climate deal on track, despite a lack of substantive progress over the past two weeks, officials and experts said.

At the meeting which ended on Thursday, negotiators slimmed down the cumbersome 90-page text of a draft deal by a few pages as the language was edited - but no options were weeded out.

A plan was agreed to consolidate the text further, and to provide more structure by late July, well before the next round of talks begin at the end of August.

A journal publisher that distributed studies written by a climate skeptic whose work was financed by fossil fuel interests has launched an ethics investigation over undisclosed funding.

The investigation byElsevier, a global network of scientific journals, was prompted by documents showing that Harvard-Smithsonian scientist Willie Soon failed to disclose industry funding in 11 studies published by nine journals.

Six of those papers were published in four Elsevier publications. Elsevier requires its authors to disclose financial conflicts that "could inappropriately influence, or be perceived to influence, their work."